Impression material

ABSTRACT

A two part impression material suitable for use as a dental impression material comprises a first part containing a product of the reaction of an alpha, beta-ethylenically unsaturated dicarboxylic acid anhydride, such as maleic anhydride, and a liquid polydiene resin, e.g. polybutadiene, and a second part containing a setting agent for the reaction product which setting agent is an alkoxylated fatty mono-amine or an alkoxylated fatty polyamine having from 2 to 30, preferably 5 to 15 moles of alkoxylate per mole of the fatty amine. The alkoxylate groups of the setting agent being one or more groups selected from the group comprising ethoxylate, propoxylate and butoxylate groups. A method of taking a dental impression using the reaction product of the first and second parts of the two part dental impression material is also disclosed.

The present invention relates to a two part impression material,suitable for use as a dental impression material, to a method ofpreparing the impression material and to a process for using the twopart impression material to obtain an impression.

British Pat. No. GB 2 027 035B discloses a two-part dental impressionmaterial comprising a first part containing a product of the reaction ofan alpha, beta ethylenically unsaturated dicarboxylic acid anhydride anda liquid polydiene resin and a second part containing a setting agentwhich has at least two reactive hydrogen atoms per molecule and iscapable of forming a cross-link between molecules of said reactionproduct. The patent states that suitable setting agents include amines,polyols, amides, alkanolamines and alkanolamides. Also included arepolyepoxides in combination with an epoxide ring-opening or carboxylicanhydride ring-opening compound.

Some of the requirements of a dental impression material are indicatedin the introduction of No. GB 2 027 035B and British StandardSpecification No. BS 4269: Part 1: 1968 specifies a number of physicalproperties required by an elastomeric dental impression material.

It has now been found that the use of certain alkoxylated setting agentsprovides impression materials having improved performance as comparedwith the dental impression materials described in No. GB 2 087 035B. Inparticular, the use of the selected setting agents enables theimpression materials to satisfy the criteria of No. BS 4269: Part 1:1968.

Thus, according to the present invention a two part impression material,suitable for use as a dental impression material, comprising a firstpart containing a product of the reaction of an alpha,beta-ethylenically unsaturated dicarboxylic acid anhydride and a liquidpolydiene resin and a second part containing a setting agent for thesaid reaction product is characterised in that the setting agent is analkoxylated fatty monoamine or an alkoxylated fatty polyamine havingfrom 2 to 30 moles of alkoxylate per mole of the fatty amine, thealkoxylate groups being one or more alkoxylates selected from the groupcomprising ethoxylate, propoxylate and butoxylate groups.

Although the two part impression material according to the presentinvention is particularly suitable for use as a dental impressionmaterial, it may be used in other applications. For example, the twopart impression material may be used to take an impression of an ear foruse in the fitting of hearing aids. Thus, although the invention will bedescribed hereinafter with particular reference to its use as a dentalimpression material this should not be taken as limiting the inventionto this application.

The present invention includes a method of preparing an impressionmaterial, particularly a dental impression material, which methodcomprises mixing together the two parts of the impression material asdescribed above and also includes the product of the reaction betweenthe first and second part of the impression material.

The invention also includes a method of taking a dental impression whichcomprises placing in a dental impression mould a dental impressionmaterial prepared by mixing together the two parts of the impressionmaterial as hereinbefore described, bringing the mould into contact withthe patient's teeth or jaws or with a dental model or prosthesis,allowing the dental impression material to set and thereafter removingthe mould to leave an impression in the dental impression material.

Alkoxylated monoamines and polyamines are known and some arecommercially available. They may be prepared by alkoxylating fattyamines by known methods. The fatty amines are preferably derived from aC₈ to C₂₂ compound containing one or more saturated or unsaturated fattyacid. More preferably, the fatty amines are derived from C₁₂ to C₁₈compounds such as, for example, oleic, lauric, palmitic or stearic acid,tallow or hydrogenated tallow, coconut oil or soya bean oil. Thealkoxylate groups are preferably ethoxylate or propoxylate groups ormixtures thereof. Preferably the setting agents have from 5 to 15 molesof alkoxylate per mole of fatty amine.

Setting agents suitable for use in the compositions according to thepresent invention include alkoxylated fatty amines having the followinggeneral formula: ##STR1## where R is a hydrocarbyl group having from 8to 22 carbon atoms

R¹ is (CH₂)₃ or CH₂ CH(CH₃)CH₂

R², R³ and R⁴ are the same or different and are H, CH₃ or CH₂ CH₃

n is 0 or a positive integer from 1 to 3

x, y and z are the same or different and are individually 0 or apositive integer from 1 to 6, the sum of x,y and z being from 2 to 30,preferably 5 to 15.

If x, y or z in the above formula is greater than 1, then the alkoxylategroup may be a mixture of alkoxylates. For example, if y=3 then (CH₂CHR³)_(y) may comprise two ethoxylate groups and one propoxylate group.

The extent of alkoxylation is the number of moles of alkoxylate per moleof fatty amin e i.e. in the above formula, the extent of alkoxylation ofa monoamine is y+z and of a diamine is x+y+z. However, in practice analkoxylated fatty amine is likely to be a mixture of amines. Thus,although x,y and z are given as integers or zero in the above formula,the extent of alkoxylation may not be an integer.

Suitable setting agents for use in the present invention include;

N,N-bis(11¹ -hydroxy-3¹ :6¹ :9¹ -trioxaundecyl)-octadec-9-enylamine

N,N¹,N¹ -tris(11¹ -hydroxy-2¹,5¹,8¹ -trimethyl-3¹ :6¹ :9¹-trioxadodecyl)N-octadec-9¹¹ -enyl-1,3-diaminopropane

N,N¹,N¹ -tris(8¹ -hydroxy-2¹,5¹ -dimethyl-3¹ :6¹ -dioxanonyl)N-octadec-9¹¹ -enyl-1,3-diaminopropane.

The most suitable alpha, beta-ethylenically unsaturated dicarboxylicacid anhydride for use in the preparation of the reaction product ismaleic anhydride.

The liquid polydiene resin may be a homopolymer of a conjugated diene ora copolymer of a conjugated diene and one or more copolymerisableethylenically unsaturated monomers. If the liquid polydiene resin is acopolymer, it preferably comprises at least 50% by weight of aconjugated diene. The polydiene resin may be prepared by knownpolymerisation methods.

The conjugated diene is preferably butadiene and an example of asuitable copolymerisable ethylenically unsaturated monomer is styrene.

The number average molecular weight of the liquid polydiene resin ispreferably from 1,000 to 10,000.

The reaction of a liquid polydiene, such as polybutadiene, and an alpha,beta-ethylenically unsaturated dicarboxylic acid anhydride, such asmaleic anhydride, is well known. A conventional method of preparingmaleinised polydiene is disclosed in British Pat. No. GB 2 027 035B. Thereaction between the liquid polydiene and the alpha-beta-ethylenicallyunsaturated dicarboxylic acid will be referred to as "functionalisation"in this specification and the reaction product will be referred to as"functionalised" polymer. Typically, the extent of functionalisation,e.g. the amount of maleic anhydride units associated with the polydiene,is from 5 to 20 parts by weight per 100 parts of the polydiene.

After functionalisation, the reaction product may be stripped by heatingunder vacuum to remove any traces of volatile material. A volatilesolvent or diluent may be added to the functionalised polymer prior tothe stripping step. The functionalised polymer may also be washed with asolvent with which it is immiscible, e.g. water, in order to removesoluble material. The final product preferably has a free maleicanhydride content of not more than 0.15% by weight.

Generally the first and/or second parts of the impression materialaccording to the present invention contain fillers, plasticisers andother additives and are in the form of a paste. Conveniently both partsof the impression material are in the form of pastes, the viscosity ofthe pastes being such that the two parts may be easily mixed together.Mixing of the two parts is generally effected by hand using a spatula orsimilar tool. The two parts may be pigmented such that they havecontrasting colours. This provides a means of visually indicating when ahomogeneous mix is achieved.

The use of fillers in the first and/or second part of the impressionmaterial affects the viscosity of the part prior to mixing and confersthe properties of opacity and/or toughness on the final impressionmaterial. The inclusion of fillers may also affect the rate of settingof the materials. As already mentioned, the viscosity of each part ofthe impression material should be such that the two parts may be easilymixed together and so the amount of filler used will be determined tosome extent by the viscosities of the other components. Typically, theproportion of filler in either or both parts of the impression materialis from 0 to 80% by weight and is conveniently from 10 to 70% by weight.The water content of the filler is preferably relatively low e.g. lessthan 0.1% by weight. A relatively high water content may adverselyaffect the storage stability of the product.

Suitable fillers include those conventionally used in dental impressionmaterials such as for example whiting, china clay, ground limestone,barytes, talc and silica.

Conventional pigments and dyes, e.g. those known for use in dentalmaterials, may be used to colour one or both parts of the impressionmaterial.

Diluents and plasticisers such as those conventionally used in polymercompositions may be included in either or both parts of the impressionmaterial.

One or both parts of the impression material may also contain a mouldrelease agent such as, for example, silicone oil.

The relative proportions of the first and second parts which are mixedtogether to form the impression material depend on a number of factorssuch as, the amount of the setting agent in the second part and theamount of the functionalised polymer and its extent offunctionalisation, the setting time required and the degree ofcross-linking required. The relative proportions are generally selectedsuch that there are at least sufficient active groups in the second partof the impression material containing the setting agent to react withall of the anhydride groups of the functionalised polymer in the firstpart. Preferably, however, the proportions are such that the amount ofsetting agent used is at least 1.5 times the stoichiometic amountrequired to react with all of the anhydride groups of the functionalisedpolymer. A practical upper limit is 4 times the stoichiometric amount.More preferably the amount of setting agent is from 1.75 to 2.25 timesthe stoichiometric amount required to react with all of the anhydridegroups of the functionalised polymer. The use of more than thestoichiometric amount of setting agent improves the tension set of thefinal impression material.

The invention is illustrated by the following examples:

EXAMPLES 1 to 10

Various setting agents were mixed with maleinised polybutadiene. Thesetting agents were ethoxylated lauryl monoamines having differentethoxylate levels, propoxylated oleyl diaminopropanes having differentpropoxylate levels and ethoxylated coconut oil diaminopropanes havingdifferent ethoxylate levels. The maleinised polybutadiene used was acommercially available product sold under the trademark LITHENE LX1610MA by Revertex Limited which contained 10 parts by weight of maleicanhydride per 100 parts by weight of polybutadiene; the polybutadienehaving a molecular weight of approximately 8000.

In each case, sufficient setting agent was mixed with the maleinisedpolybutadiene to react with substantially all of the anhydride groups ofthe functionalised polymer.

The components were easily mixed together using a spatula to produce ahomogeneous blend.

The working time of each composition was determined. This was done bymeasuring the time from the start of mixing to the commencement ofsetting. The commencement of setting was taken to be the point at whicha filament could not be drawn out of the mixture with a spatula. TheIRHD hardness of some of the compositions was measured 10 mins and 30mins from the start of mixing.

The results given in Table 1 show that for any particular fatty amine,increasing the alkoxylate level increases the working time, but tends toreduce the hardness.

The compositions of Examples 2, 3, 5, 8, 9 and 10 have working timeswhich are not less than the minimum working time specified in BS 4269.The other examples are included to show how the working time varies withalkoxylate level. Impression materials having working times less thanthe minimum specified in BS 4269 may have uses in applications otherthan for dental impressions.

                                      TABLE 1    __________________________________________________________________________    Effect of Alkoxylate Level on Working Time and Hardness                                    Working                                         Hardness                             Extent of                                    Time (Minutes from mixing time)    Example         Setting Agent       Alkoxylation                                    (mins)                                         10     20    __________________________________________________________________________    1    Ethoxylated lauryl monoamine                             5      1.0  35     52    2    "                   10     2.8  28     43    3    "                   15     3.7  28     34    4    Ethoxylated coconut oil diamino propane                             15     1.1  42     60    5    "                   20     1.5  42     56    6    Propoxylated oleyl diamino propane                             3      0.58    7    "                   7      1.08    8    "                   8      1.25    9    "                   9      1.42    10   "                   12     2.10    __________________________________________________________________________

EXAMPLES 11 to 20

Examples 1 to 10 were repeated except that the maleinised polybutadieneused was Lithene N₄ 5000 1OMA ex Revertex Limited. The polybutadiene ofthis material has a molecular weight of approximately 5000. The workingtimes for these compositions are given in Table 2 and show, bycomparison with the results given in Table 1, that a reduction in themolecular weight of the polydiene increases the working time.

                  TABLE 2    ______________________________________    Effect of polydiene molecular weight on working time    Ex-                        Extent of                                        Working    am-                        Alkoxyl- Time    ple  Setting Agent         ation    (mins)    ______________________________________    11   Ethoxylated lauryl monoamine                               5        1.3    12   Ethoxylated lauryl monoamine                               10       3.6    13   Ethoxylated lauryl monoamine                               15       4.8    14   Ethoxylated coconut   15       1.2         oil diamino propane    15   Ethoxylated coconut   20       1.8         oil diamino propane    16   Propoxylated oleyl diamino propane                               3        0.83    17   Propoxylated oleyl diamino propane                               7        1.67    18   Propoxylated oleyl diamino propane                               8        1.92    19   Propoxylated oleyl diamino propane                               9        2.33    20   Propoxylated oleyl diamino propane                               12       4.0    ______________________________________

EXAMPLES 21 TO 25

Different fillers were mixed with maleinised polybutadiene, Lithene N₄5000 10MA. An ethoxylated oleyl monoamine setting agent having anethoxylate level of 8 was then added to each polymer/filler mixture andthe working time and hardness of each composition determined as inExamples 1 to 10. The results are given in Table 3.

                  TABLE 3    ______________________________________                                  Hardness                 Amount of                         Working  (Mins after                 Filler  Time     mixing time)    Example           Filler      (% wt/wt) (mins) 10   30    ______________________________________    21     Calcium     25         3.25  34   65           carbonate           Talc        25    22     Glass        7        3.2    29   38           microspheres    23     Micronised  22        3.8    28   28           polypropylene    24     China clay  24        4.0    28   38    25     Microsilica 12        3.5    28   34    ______________________________________

EXAMPLE 26

A two part dental impression material according to the present inventionwas prepared by mixing together the following components to form a firstpart and a second part:

    ______________________________________                    Parts by weight    ______________________________________    First Part    Maleinised polybutadiene                      46    Filler            41    Release agent     10    Plasticiser       3    Second Part    Alkoxylated fatty amine                      50    Filler            50    Dye               0.025    ______________________________________

The maleinised polybutadiene used was the reaction product of maleicanhydride and liquid polybutadiene sold by Revertex Limited under thedesignation LITHENE LX16 10MA (LITHENE is a trademark). The molecularweight of the polybutadiene was approximately 8000 and the polymercontained 10 parts by weight of maleic anhydride per 100 parts by weightof polybutadiene.

The filler included in the first part of the composition was grounddolomite sold under the trade mark MICRODOL Extra by Norwegian Talc (UK)Ltd. The filler had a moisture content of approximately 0.05% by weight.

The release agent used was a silicone fluid sold by Dow Corning Ltdunder the designation DC 550.

The plasticiser was a dioctyl adipate sold by BP Chemicals Limited underthe trade name BISOFLEX DOA (BISOFLEX is a registered trade mark).

The alkoxylated fatty amine was a propoxylated oleyl diamino propane.The extent of propoxylation i.e. the number of moles of propoxylate permole of oleyl diaminopropane was 12±0.4.

The filler used in the second part of the composition was calciumcarbonate sold under the trade name CALOFORT S by John & E SturgeLimited.

The dye used to colour the second part of the composition was an oilsoluble red dye having the colour index (1971) reference Solvent Red 23No 26100. The first part of the composition had a viscosity of 180 PaSat 25° C.

The first part and second part were mixed together in the volume ratioof 2:1. These proportions provided 1.77 times the stoichiometric amountof setting agent required to react with all of the anhydride groups ofthe maleinised polybutadiene.

The properties of the mixed composition were as follows:

Working time: 4 mins

Setting time: 10 mins

Tension set: 2.5%

Elongation: at break: 230%

Dimensional stability: 0.1%

International Rubber Hardness: (30 mins) 40

The properties were determined according to BS4269:Part 1 1968 exceptfor the International Rubber Hardness which was determined according toASTM D 1415-68.

The working time and setting time were within the limits set by BS4269for a regular set material. The tension set was also acceptable in termsof the limits set by the British Standard for polysulphide dentalimpression materials.

The British Standard states that the elongation at break of the materialshould be greater than 50% and the dimensional stability should be notmore than ±0.2%. Thus the impression material according to the presentinvention had the properties of an acceptable dental impression materialas defined by BS 4269.

EXAMPLE 27

A two part dental impression material was prepared substantially asdescribed in Example 26 except that the proportions of the components ofthe first part of the composition were;

Maleinised polybutadiene: 46

Filler: 47

Release agent: 5

Plasticiser: 2

The setting agent used in the second part of the impression material wasbased on a commerically available fatty amine and was a propoxylatedoleyl diaminopropane alkoxylated to a Ievel of approximately 10.5 to11.0. Apart from this, the second part of the impression material was asfor Example 26.

The first part had a viscosity of 340 Pa.s at 25° C. The first part andsecond part were mixed together in the volume ratio of approximately2:1. These proportions provided approximately 1.9 times thestoichiometric amount of setting agent required to react with all of theanhydride groups of the maleinised polybutadiene. The impressionmaterial was found to have the following properties.

Working time: 2.5 mins

Setting time: 6 mins

Tension set: 1.5%

Elongation at break: 190%

Dimensional stability: 0.1%

International Rubber Hardness: (30 mins) 35

This composition was less fluid than the composition according toexample 26 and was somewhat easier to handle.

The impression material had a working time and setting time within thelimits set by BS 4269 for a regular set material and as for Example 26,the tension set, elongation at break and dimensional stability were wellwithin the limits set by the British Standard.

A dental impression was successfully obtained using this composition.After washing and drying the impression it was filled with dentalplaster and a cast obtained.

EXAMPLE 28

A two part dental impression material was prepared as described inExample 27 except that the alkoxylated fatty amine setting agent used inthe second part of the composition had a level of propoxylation of9.0±0.4 rather than 12 or 10.5 to 11.0 as in Examples 26 and 27.

When the first part, which was the same as for Example 27, and themodified second part were mixed together in the volume ratio ofapproximately 2:1. These proportions provided approximately 2.13 timesthe stoichiometric amount of the setting agent required to react withall of the anhydride groups of the maleinised polybutadiene. Theimpression material was found to have the following properties:

Working time: 1.7 mins

Setting time: 5.25 mins

Tension set: 1 to 1.5%

Elongation at break: 150%

Dimensional stability: 0.04%

International Rubber Hardness: (30 mins) 36

The working time and setting time were faster than for Example 27 andthe material would be a quick set material. The tension set, elongationat break and dimensional stability were once again well within thelimits set by the British Standard.

A dental impression was sucessfully obtained using the composition and aplaster cast was made from the impression. The dental impression wasthen copper plated using conventional techniques. A plaster cast wastaken from the copper plated impression and the copper was successfullytransferred to the plaster cast.

By adding 10% by weight of additional plasticiser to the composition, asyringeable dental impression material was obtained which had a useabletime of up to 1.6 min and a set time of 5.5 minutes.

EXAMPLE 29

A two part dental impression material according to the present inventionwas prepared comprising:

    ______________________________________                    Parts by weight    ______________________________________    First Part    Maleinised polybutadiene                      45.3    Filler            42.1    Release agent     7.8    Plasticiser       4.8    Second Part    Alkoxylated fatty amine                      50.0    Filler            50.0    Dye               1.0    ______________________________________

The maleinised polybutadiene, fillers, release agent and plasticiserwere the same as those used in Example 26. The alkoxylated fatty axinewas the same as that used in Example 28. The dye was Red No 30 Lake.

The first part and second part were mixed together in the volume ratioof 2:1. These proportions provided approximately 2.16 times thestoichiometric amount of the setting agent required to react with all ofthe anhydride groups of the maleinised polybutadiene. The impressionmaterial had the following properties.

Working time: 2.3 mins

Setting time: 5.5 mins

Tension set: 2.0-1.5

Elongation at break: 210

International Rubber Hardness: 30

This impression material was successfully used as a syringeable gradedental impression material and was also used, without modification, in adental tray to prepare a dental impression.

We claim:
 1. A two part impression material, suitable for use as adental impression material, comprising a first part containing a productof the reaction of an alpha,beta-ethylenically unsaturated dicarboxylicacid anhydride and a liquid polydiene resin, and a second partcontaining a setting agent for the said reaction product, characterisedin that the setting agent is an alkoxylated fatty mono-amine or analkoxylated fatty polyamine having from two to thirty moles ofalkoxylate per mole of the fatty amine, the alkoxylate groups being oneor more alkoxylates selected from the group comprising ethoxylate,propoxylate and butoxylate groups.
 2. An impression material as claimedin claim 1 in which the setting agent is derived from a compositioncomprising one or more saturated or unsaturated fatty acids having from12 to 18 carbon atoms.
 3. An impression material as claimed in claim 2in which the setting agent is derived from one or more compositionsselected from the group comprising oleic acid, lauric acid, palmiticacid, stearic acid, tallow acid, hydrogenated tallow acid, coconut oiland soya bean oil.
 4. An impression material as claimed in any of claims1 to 3 in which the alkoxylate groups of the setting agent areethoxylate groups, propoxylate groups or mixtures thereof.
 5. Animpression material as claimed in any of claims 1 to 4 in which thesetting agent is an alkoxylated monoamine or polyamine having from 5 to15 moles of alkoxylate per mole of fatty amine.
 6. An impressionmaterial as claimed in any of claims 1 to 5 in which the setting agentis an alkoxylated mono- or poly- amine having the general formula;##STR2## where R is a C₈ to C₂₂ hydrocarbyl group,R₁ is (CH₂)₃ or CH₂CH(CH₃)CH₂, R₂, R₃ and R₄ are the same or different and are selectedfrom H, CH₃, and CH₃ CH₂ n is 0 or a positive integer from 1 to 3 andx,y and z are the same or different and are individually 0 or a positiveinteger from 1 to 6, the sum of x,y and z being from 2 to
 30. 7. Animpression material as claimed in claim 6 in which the setting agent isN,N¹,N¹ -tris(8¹ -hydroxy-2¹,5¹ -dimethyl-3¹ :6¹-dioxanonyl)N-octadec-9¹¹ -enyl-1,3-diaminopropane.
 8. An impressionmaterial as claimed in any of claims 1 to 7 in which the first partcontains a product of the reaction of maleic anhydride and a homopolymeror copolymer of polybutadiene.
 9. An impression material as claimed inclaim 8 in which the reaction product comprises from 5 to 20 parts byweight of maleic anhydride per 100 parts of the polybutadiene.
 10. Animpression material as claimed in any of claims 1 to 8 wherein the firstpart and/or second part is in the form of a paste and contains up to 80%by weight of filler.
 11. A two part impression material, suitable foruse as a dental impression material, according to claim 1 in which thefirst part comprises (a) maleinised polybutadiene, (b) a filler, (c) arelease agent and (d) a plasticiser and the second part comprises (a) apropoxylated oleyl diaminopropane, propoxylated to a level of from 5 to15 and (b) a filler.
 12. A method of preparing an impression material,suitable for use in taking dental impressions, comprises mixing togetherthe first part and the second part of the two part impression materialas claimed in any of claims 1 to
 11. 13. A method as claimed in claim 12in which the amount of the second part mixed with the first part is suchthat the amount of setting agent is from 1.5 to 4 times thestoichiometric amount required to react with all of the anhydride groupsof the reaction product of the first part.
 14. A method as claimed inclaim 13 in which the amount of the second part mixed with the firstpart is such that the amount of setting agent is from 1.75 to 2.25 timesthe stoichiometric required to react with all of the anhydride groups ofthe reaction product of the first part.
 15. An impression material,suitable for use as a dental impression material, comprising the productof the reaction between the first part and the second part of a two partdental impression material as claimed in any of claims 1 to
 11. 16. Animpression material as claimed in claim 15 which is the product of thereaction between the first part and an amount of the second part whichcontains from 1.5 times to 4 times the stoichiometric amount of settingagent required to react with all of the anhydride groups of the reactionproduct in the first part.
 17. An impression material as claimed inclaim 16 which is the product of the reaction between the first part andan amount of the second part which contains from 1.75 times to 2.25times the stoichiometric amount of setting agent required to react withall of the anhydride groups of the reaction product in the first part.18. A method of taking a dental impression which comprises placing in adental impression mould an impression material prepared according to themethod as claimed in any of claims 12 to 14, bringing the mould intocontact with the patient's teeth, or jaws or with a dental model orprosthesis, allowing the dental impression material to set andthereafter removing the mould to leave a impression in the dentalimpression material.